Firstly, I want to take time to thank you for having the patience to answer my question.  Now to reply your questions: You are right. I am using P7

1. Yes, when I do still rendering, the image comes out ok
2. The renderers I've used are Preview, Fly, P4 and sketch and they all came out with the same problem. The only exception of course is sketch which did not even have a background image at all except little sketches.
3. I do not know how to determine if the image or aspect ratio is the same with the renderer but what I can tell you is that when I imported the background image into Poser, I made the window mach the image size.

I look forward to your reply. Thank you